Companies providing content via the Internet generally seek to lower the cost of doing so while providing high availability. Some content providers may also seek to customize the content provided. Customization can include watermarking content, inserting digital rights management signatures, or other user-specific customizations. Providing customized content generally makes delivering the content more expensive since the customization must be done under the control of the content provider and from delivery points under the control of the provider.
Content delivery networks are delivery systems with geographically dispersed networks of servers. Servers at various locations each store a copy of content and clients requesting the content are routed to the nearest location so the content is delivered with the best possible performance and/or the lowest possible cost. To achieve the best possible performance, the edge locations are typically high performance data centers that are able to respond to requested loads during peak times. To achieve lower cost, techniques are used to direct content delivery requests to servers which may not be under peak load or may be in a data center with a lower cost of operation.
Each server location contains an identical copy of content available from other servers in the content delivery network. This generally makes such networks unsuitable for customization of the delivery of each individual content objects provided to users. Customization of content at each of the servers works against maintaining identical copies in a state ready for delivery to a user. Customizing content in a content delivery network is more difficult where the content delivery network is not maintained by the content provider, but rather a service provider.